1. Field of the Invention
The present invention relates to a stereolithographic resin composition, and a stereolithographic method using said resin composition. More specifically, the present invention relates to a stereolithographic resin composition which enables the production of high-precision moldings having superior mechanical strength, and a stereolithographic method using said resin composition.
2. Related Art
A stereolithographic method is a technique, as described in Japanese Patent Application Laid-open No.SHO 60-247515, wherein a given portion of photo-curing resin placed in a vessel is exposed continuously to a beam such as argon, helium-cadmium or semiconductor laser from above to cure the exposed portion, in order to produce a desired plane of cured layer. Then the cured layer is overlaid with another layer of the photo-curing resin, which is then photo-cured in the same manner to produce a second cured layer which continuously overlaps the first layer; and the same process is repeated to finally obtain a desired three-dimensional solid shape.
A type of resins previously used for the above-described stereolithographic method are radically polymerizing resin compositions, including photosensitive resins composed primarily of polyester acrylate, urethane acrylate, epoxy acrylate, or polyether acrylate. For example, Japanese Patent Application Laid-open No.HEI2-145616, with the aim of reducing deformation, discloses a stereolithographic resin which contains liquid resin and fine particles whose difference in apparent specific gravity is less than 0.2. Japanese Patent Application Laid-open No.HEI2-208305 discloses a resin composition containing a reactive oligomer and a high content of a specific bifunctional acrylate. For producing moldings at higher precision, Japanese Patent Applications Laid-open No.HEI3-15520 reports a composition comprising an unsaturated ethylene-derivative monomer, a photo-initiator, and a potentially insoluble, potentially radioactive polarizing substance, and Japanese Patent Applications Laid-open No.HEI3-41126 reports a composition comprising an unsaturated ethylene-derivative monomer, a photo-initiator, and a potentially soluble radio-polarizing substance, respectively. In addition, Japanese Patent Application Laid-open No.HEI4-85314 a resin composition comprising a silicone urethane acrylate, a compound having multifunctional ethylene-type unsaturated bonds, and a polymerization initiator.
Another type of stereolithographic resins are known cationically polymerizing resins. For example, Japanese Patent Application Laid-open No.HEI1-213304 discloses an invention characterized by comprising a cationically polymerizing energy beam curable organic compound and a energy sensitive cationic polymerization initiator. Japanese Patent Application Laid-open No.HEI2-28261 discloses a resin comprising a cationically polymerizing energy beam curable organic compound and a portion of a radically polymerizing radio-curing organic compound, which exhibits reduced shrinkage and improved resolution. Also, Japanese Patent Application Laid-open No.HEI2-80423 discloses a resin composition comprising an epoxy resin, a vinyl ether resin, a energy beam sensitive cationic polymerization initiator, a radically curing resin, and a energy beam sensitive radical polymerization initiator. In addition, Japanese Patent Application Laid-open No.HEI2-75618 discloses a stereolithographic resin composition characterized by comprising a cationically polymerizing energy beam curable organic compound, a energy beam sensitive cationic polymerization initiator, a radically polymerizing energy beam curable organic compound, a energy beam sensitive radical polymerization initiator, and a polyester having hydroxyl groups.
However, existing stereolithographic resins do not provide sufficient mechanical strength against impacts on the moldings. The fragileness of the moldings made their application as mechanical parts difficult, as they easily cracked when struck. Another hindrance in using photo-curing resins as a stereolithographic resins is the significant volumetric shrinkage during curing, which results in the warp and distortion of the moldings.
The object of the present invention, therefore, is to provide a stereolithographic resin composition having improved strength against the moldings, and a stereolithographic method using said resin composition.
Another object of the present invention is to provide a stereolithographic resin composition having reduced volumetric shrinkage to prevent warp and distortion during curing, and a stereolithographic method using said resin composition.